The present invention is directed to bicycle control cable systems and, more particularly, to an apparatus for guiding a control cable from a controlling device such as a brake lever or shift lever to a controlled device such as a brake or transmission.
Bicycle control devices typically use control cables of the type having an inner wire that slides within an outer casing. One end of the inner wire is connected to a controlling device such as a brake lever, shift lever, twist-grip control device, etc. mounted on the bicycle handlebar, and the other end of the inner wire is connected to a controlled device such as a brake or transmission located at some distance from the controlling device. Because the controlled device is located at some distance from the controlling device, the control cable typically must be routed along the bicycle frame and fastened to the frame so that the control cable does not interfere with the rider or with other bicycle components. FIG. 1 shows a typical cable routing scheme wherein an outer casing 10 of a control cable 14 originating at a controlling device (not shown) mounted to a handlebar 16 is stopped at a cap receiver 18 brazed to the bicycle frame 22. The inner wire 26 exits the outer casing 10 at cap receiver 18 and proceeds to the rear of the bicycle. If the control cable 14 is used to control a derailleur, for example, then the inner wire 26 will enter another portion of the outer casing (not shown) stopped at another cap receiver (not shown) located at the rear of the bicycle. The control cable 14 then will be routed to the derailleur.
As shown in FIG. 1, the control cable 14 typically bends as it proceeds to the cap receiver 18 in order to accommodate obstructions such as the head tube and bearing assemblies. Unfortunately, bends in the control cable decrease the force transmission efficiency of the control cable because of friction between the inner wire and the outer casing. For example, one bend in the control cable can decrease the force transmission efficiency by 10%, two bends in the control cable can decrease the force transmission efficiency by 20%, and three bends in the control cable (the situation shown in FIG. 1) can decrease the force transmission efficiency by 30%. If the control cable bends again at the rear of the bicycle, for example, at the seat tube, then the total of four bends can decrease the force transmission efficiency by 35%. Such decreases in the force transmission efficiency are of great concern to the manufacturer of the controlling and controlled devices, since poor performance of the controlling and controlled devices often is blamed unjustly on the quality of the manufacturer's products and not on the bends in the cable system. Unfortunately, the location of the cap receivers on the bicycle as well as the geometry of the frame are determined by the frame manufacturer, so the manufacturer of the controlling and controlled devices has no control over the number of bends in the control cable when the control cable is attached to the bicycle frame. Even if the frame maker places the cap receivers on the side of the bicycle frame, such as cap receiver 30 shown in FIG. 1, the control cable still must bend around the head tube before the control cable can be attached to the cap receiver, thus again resulting in three bends in the control cable. Furthermore, such cap receiver placement does not overcome the problem of bends in other frames having a different geometry.